What's eating my water horsetail?

Water Horsetail is exceptionally pest-resistant — its high silica content deters most insects and grazers. Aphids occasionally colonise stems in warm spells, and moth or sawfly larvae may chew tips in summer. Muskrats and geese graze emergent stems in large stands but rarely cause lasting harm to established colonies.

Soft colonies on stem tips, secreting sticky honeydew; localised yellowing and weakened new growth Dislodge with a strong water jet; apply insecticidal soap to affected stems; natural predators (ladybirds, hoverflies) usually keep numbers in check

Chewed or clipped stem tips; occasional defoliation of individual shoots in summer Hand-pick caterpillars when populations are low; Bacillus thuringiensis (Bt) spray is effective against young larvae before they grow large

Stems bitten off at water level or uprooted; noticeable reduction in stand density in late summer or autumn Physical barriers (wire mesh around container plantings); planting in deeper water where access is harder; established colonies generally recover vigorously